1. Field of the Invention:
The present invention relates to the field of medical devices for removing calculi, and particularly to such devices for use in percutaneous procedures.
2. Description of the Prior Art:
Instruments for removing calculi, for example, kidney and gallstones, without major surgery, are commonly of two general types. One takes the form of an expandable basket, and the other consists of miniaturized grasping forceps. Such instruments are typically inserted through endoscope passages and through naturally or artificially-formed body passages. One problem associated with both types of instruments lies in the possible injury to surrounding tissue as a grasped stone is extracted through the body passage or organ. Such dangers may be reduced by fragmenting the stone in situ by lithotripsy. However, such fragmentation may create additional problems if fragments remain and provide the nuclei for further stone development. During shattering, fragments can pass out of view, such as into lateral branches of the kidney cavity, and can thus be overlooked.
It has been known in the art that there are advantages in providing a means by which stone fragments produced in situ are contained in a confined area. For example, in U.S. Pat. No. 4,696,297, issued to Pleines, et al. on Sept. 29, 1987, there is described a method for encapsulating the stone fragments in a gel to prevent their escape. According to the Pleines procedure, a flowable gelatin solution is introduced into the body cavity so that the stone to be shattered is embedded therein. As a result of the cooling of the solution, a solid gel is formed in which the stone is enclosed. The stone is then shattered and the fragments remain within the gel to be thereafter collected and removed. The gel is then liquified and the gelatin solution also removed.
In U.S. Pat. No. 4,611,594, issued to Grayhack, et al. on Sept. 16, 1986, there is described a medical instrument for containment and removal of calculi. The Grayhack Patent discloses several embodiments for such an instrument. In one embodiment, a catheter has an expandable distal end within which a stone, held for example by a typical stone basket, can be drawn within and enclosed thereby. In a second embodiment, a catheter includes several struts which extend outwardly from the distal end, and a webbing is secured to and supported by the struts. The struts and webbing are normally positioned in an open configuration, but are forced closed when the catheter and struts are pulled into a second, outer catheter. In a third embodiment, the struts and supported webbing are secured to an inner catheter, and are normally maintained in a closed position. Guide wires are secured to another catheter and are operable to pull the struts and webbing outwardly into an open condition for receipt of a stone basket and contained stone. Similarly in a fourth embodiment, the struts and webbing are secured to an inner catheter and a control webbing is secured to an outer catheter to pull the normally closed struts into an open condition. In each of the embodiments described in the Grayhack, et al. Patent, the webbing is secured only to the supporting struts and the associated catheter, and forces are applied from externally of the webbing and struts to either push the normally open struts closed, or to pull open the normally closed struts.
Several catheter designs in the prior art have employed end balloons for encapsulating objects adjacent the tip of the catheter. Devices of this type are shown, for example, in U.S. Pat. Nos. 4,324,262, issued to Hall on Apr. 13, 1982; 4,469,100, issued to Hardwick on Sept. 4, 1984; and, 4,243,040 issued to Beecher on Jan. 6, 1981. Catheters having umbrella or parachute type configurations for collecting materials, as the catheters are drawn longitudinally, are disclosed in U.S. Pat. Nos. 3,472,230, issued to Fogarty on Oct. 14, 1969; and, 4,790,812 issued to Hawkins, Jr., et al. on Dec. 13, 1988.